1. Field of the Invention
The present invention relates to a liquid crystal display device and particularly to a novel structure capable of infallibly light-shielding a reverse region and enhancing an aperture ratio.
2. Description of Prior Art
For example, a liquid crystal display device that is one of planar display devices has been utilized in various fields, such as OA equipment, information terminals, watches, television sets, etc., because it has features of lightweight, small thickness, low power consumption, etc. In particular, since a liquid crystal display device using a thin film transistor device (TFT device) is excellent in response, it has been used as a display device in a great number of electronic devices including mobile telephones, television sets, computers, etc.
In the liquid crystal display device, an array substrate and an opposing substrate are disposed face to face at a prescribed interval to constitute a liquid crystal cell. In an active matrix liquid crystal display device, for example, pixel electrodes disposed in a matrix manner on an array substrate causes liquid crystal materials injected into the liquid crystal cell to be driven, thereby displaying images, letters, etc.
In the meantime, in the active matrix liquid crystal device, the array substrate is formed thereon with a scan line and signal lines disposed in rows and columns. Thin film transistors are disposed as switching devices at the intersections between the scan line and the signal lines. The switching devices drive the pixel electrodes. In addition, the array substrate is also formed thereon with an auxiliary capacitance line for retaining applied voltage for the pixel electrodes.
When adopting the configuration described above, there arises a so-called reverse tilt domain problem to necessitate the reverse region to be light-shielded. The reverse tilt domain is a domain caused by the inversion of pretilt angle resulting from an orientation disturbance of a liquid crystal produced by an electric field between adjacent pixel electrodes when performing a gate line inversion drive or a source line inversion drive, a dot inversion drive, etc. and constitutes a case of deteriorating the visual quality.
In view of the above, studies have been made on the concealment of the reverse tilt domain to prevent a decrease in visual quality, and superposition of pixel electrodes and signal lines is utilized to light-shield the reverse region (refer, for example, to JP-A HEI 10-104664 and JP-A 2001-318390).
In the invention described in JP-A HEI 10-104664, the width of superposition between the pixel electrode and the gate signal line positioned in the orientation direction of the liquid crystal molecules is made larger than that positioned in the inverse direction, and the width of superposition between the pixel electrode and the source signal line positioned in the orientation direction of the liquid crystal molecules is made larger than that in the inverse direction, to suppress a decrease in aperture ratio and make the visual quality excellent.
JP-A 2001-318390 discloses an active matrix liquid crystal display device wherein the side edge of a display pixel electrode disposed between a pair of adjacent image signal lines is superposed on the side edge of each image signal line, the width of superposition of one of the image signal lines is made larger than that of the other image signal line, and the other image signal line is connected via a switching device to the corresponding display image electrode. It further discloses that an auxiliary capacitance line is provided with a shield electrode on which a peripheral part of the display pixel electrode is superposed.
When adopting the configuration in which the pixel electrode is superposed on the signal line to light-shield the reverse region, as described in each of the prior art references, a decrease in aperture ratio is unavoidable. Particularly, when the width of the superposition between the pixel electrode and the signal line is made wider, it is the problem how the aperture ratio should be made large.
The present invention has been proposed in view of the above problem, and the object thereof is to provide a liquid display device capable of minimizing the decrease in aperture ratio and excellent in visual quality.